MeshViewer : Camera update and small object tweak.
             ortho to perspective transition is now perfect.

to get M_PI from the platform headers and cast it to float.

compilation time for very little benefit and maybe even confusion.

functions; also remove a lot of idiotic "using namespace std" from the
codebase.

to the Tait-Bryan angles we had for now). Also, change quaternion storage
order to wxyz in order to match the constructors.

more unit tests for the quaternion to 3×3 matrix conversion.

with the unit tests.

Euler angles to a rotation matrix. Also fix quat::rotate() which was not
building the correct quaternion.

mathematical writing, and add static constructors to create quaternions
from a rotation.

code for all matrices.

"shader" source directory since we have "gpu".

the matrix code itself.

to avoid common programming errors.

reuse the linear operations in quaternions. Also mark some constructors
explicit to better spot coding errors.

function use degrees rather than radians.

cross product, normalize, etc.

According to David Turner, “it should be the only thing that NDK users
should be testing again.”